1. Field of the Invention
The present invention relates to a speech signal processing apparatus.
2. Description of the Related Art
If a user does another work while using a mobile phone, the user might use a hands-free set so as to use both hands freely.
As the hands-free set, there are known a head set provided with an earphone and a microphone, an earphone microphone, an earphone microphone of such a type as to receive sound emitted in the ear (See Japanese Patent Laid-Open Publication No. 2006-287721 and Japanese Patent Laid-Open Publication No. 2003-9272) and the like.
In a microphone of the above-mentioned headset provided with an earphone and a microphone and an earphone microphone, a noise around the user might mix into a sound uttered by the user. Thus, in a noisy environment, sound quality during a call is degraded so that even the call itself might become difficult. On the other hand, the earphone microphone of such a type as to receive sound in the ear is worn by the user in the ear, and a sound output from an eardrum of the user is converted into an electric speech signal. Thus, even in the noisy environment, the call itself would not become difficult. However, the sound output from the eardrum is different in frequency characteristics from the sound uttered from the mouth in general, and the sound output from the eardrum becomes a so-called inward sound. As a result, in the case of using the earphone microphone of such a type as to receive the sound in the ear, the sound quality during a call is inferior in general to that in the case of using the headset provided with an earphone and a microphone and an earphone microphone, particularly in a quiet environment.